Sound transmission



Dec. 29, 1936. R N 2,065,578

SOUND TRANSMISSION Filed Aug. 14, 1935 6 Sheets-Sheet l KIM KW 19% ENTORATTURNEYS Dec. 29, 1936 R, R N 2,065,578

SOUND TRANSMI SS ION Filed Aug. 14, 1935 6 Shets-Sheet 2 4 hm; m g WArroauzys Dec. 29, 1936.

R. R. GLEN SOUND TRANSMISSION Filed Aug. 14, 1955 6 Sheets-Sheet 3INVENTOR Dec. 29, 1936. R. R. GLEN SOUND TRANSMISSION Filed Aug. 1.4,1935 6 Sheets-Sheet 4 I A rg RN 2Y5 6 Sheets-Sheet 5 NV E-NTOR W /WUJMR. R. GLEN SOUND TRANSMISSION Filed Aug. 14, 1935 Dec. 29, 1936.

R. R. GLEN SOUND TRANSMISSION Dec. 29, 1936.

Filed Aug. 14, 1935 6 Sheets-Sheet 6 W /mv mm Efmmmli Patented Dec. 29,1936 UNITED STATES PATENT OFFICE SOUND TRANSMISSION Application August14, 1935, Serial No. 36,076

In Great Britain May 30, 1935 25 Claims.

This invention relates to a method and apparatus for modifying sound. Itis frequently found desirable to modify sounds which are beingelectrically transmitted for recording or re- 5 production in order toprovide a more pleasing or realistic final result. Thus, for example, itmay sometimes be desirable to modify, in the recording of sound for usein combined sound and cinematograph records, the voice of an artist whois particularly suitable for the picture record but whose voice in itsnatural form is not suitable for the sound record. It is accordingly anobject of the present invention to provide a method of modifying thetone quality of sounds being electrically transmitted for recording orreproduction and also to provide apparatus for use in this method.

The invention provides the method of modifying the tone quality ofsounds being trans- 20 mitted as electrical impulses for recording orreproduction which comprises the steps of converting the electricalimpulses into sound waves in a resonance chamber, adjusting the acousticcharacteristics of the chamber and reconverting the sound waves intoelectrical impulses.

In one form of the invention the electrical impulses are converted intosound waves by means of a loudspeaker at one end of a resonance chamberof tubular form and are reconverted into electrical impulses by amicrophone at the other end of the resonance chamber and the adjustmentof the acoustic characteristics of the chamber is effected by varyingits length.

Owing to the fact that a single loudspeaker is incapable of reproducingcorrectly the full range of sounds normally required for recording orreproduction it is preferred according to the invention to employ forconverting the electrical impulses into sound waves two or moreloudspeakers supplied from the same electrical circuit and havingdifferent sound reproducing characteristics suited more particularly todifferent parts of the sound range to be recorded or reproduced.

A further object of the invention is to provide a method and apparatuswhereby sounds from a plurality of spaced sources may be satisfactorilycombined for recording or transmission. A still further object is toprovide in one form of the invention a method and apparatus whereby anydesired balance in the combined sound of the sounds from the individualsources may be obtained.

The invention accordingly includes the method of combining for purposesof simultaneous re- (Cl. 181-B.5)

cording or transmission by electrical means sounds from a plurality ofspaced sources which comprises the steps of converting the sounds fromthe said sources separately into electrical impulses, separatelyamplifying the electrical impulses corresponding to each source,separately converting the amplified impulses from each source into soundwaves within a single chamber and re-converting the combined sound waveswithin the chamber into electrical impulses.

Preferably the electrical impulses corresponding to each source areseparately amplified or modulated to an extent sufficient to produce thedesired balance in the final combined sound.

A still further object of the invention is to provide a method andapparatus whereby the quality of sounds from several sound sources maybe individually modified before the sounds are combined or whereby thequality of the combined sound may be modified after combination.

The invention includes apparatus for modifying the tone quality ofsounds being transmitted as electrical impulses for recording orreproduction and comprising a chamber adjustable as to its acousticcharacteristics, a soundreproducing device arranged to convertelectrical impulses into sound waves within the chamber and a microphonearranged to pick up the sound waves within the chamber and to convertthem into electrical impulses. In the preferred form of the apparatusthe chamber is of tubular form and is adjustable in length to vary itsacoustic characteristics, the sound reproducing device comprises aloudspeaker located at one end of the chamber and the microphone islocated at the other end of the chamber. A plurality of loudspeakers maybe employed within the chamber.

The invention also includes apparatus for use in combining-for purposesof simultaneous recording or transmission by electrical means soundsfrom a plurality of spaced sources comprising a plurality of microphonesplaced adjacent to the several sources respectively, ampliflers arrangedto amplify the electrical impulses from each microphone individually, achamber,

a plurality of loudspeakers each arranged to convert the amplifiedimpulses from a different microphone into sound waves within thechamber, electrical connections between the microphones, amplifiers andloudspeakers and a microphone arranged to pick up the sound waves within the chamber.

Some specific arrangements of apparatus according to the invention andthe methods of using this apparatus will now be described by way ofexample and with reference to the accompanying diagrammatic drawings inwhich:--

Figure 1 is an elevation, partly in section of the apparatus employed inmodifying the quality of sound from a single source,

Figure 1A is a view of a portion of the chamber shown in Figure 1 andillustrates a modification thereof,

Figure 2 is a modification of the arrangement shown in Figure l in whichtwo loudspeakers are employed having different sound reproducingcharacteristics,

Figure 3 is a diagram illustrating the arrangement of the apparatusemployed in combining sound from a plurality of separate sources,

Figure 4 is a view partly in section of the resonance chamber andassociated loudspeakers employed in the arrangement shown in Figure 3.

Figure 5 is an end view of Figure 4 also partly in section,

Figure 6 is a longitudinal section of one of the loudspeaker extensionsshown in Figure 4 and showing the relative internal diameters atintervals along the length of the extension,

Figure 7 is a section on the line 1-.' in

Figure 6,

Figure 8 is a section on a reduced scale on the line 8-8 in Figure 7,

Figure 9 is a view showing a spring used in the bayonet form ofattachment between the extensions and the resonance chamber shown inFigure 4, and

Figure 10 is a part view of the chamber shown in Figure 4 andillustrating modified forms of the extensions.

Like reference numerals indicate like parts throughout the severalfigures of the drawings.

The arrangement shown in Figure 1 illustrates the application of theinvention to the electrical recording on a photographic film of soundsproduced on a film set. A microphone I is located on the set and iselectrically connected to an amplifier 2 which is connected to aloudspeaker 4 disposed at one end of a closed cylindrical resonancechamber 6. The loudspeaker is of any suitable type, for example, thatdescribed in my copending application for Letters Patent of the UnitedStates, Serial No. 748,474 where the driven cone has a diameter of about11 inches. The loudspeaker is detachably secured to the end of theresonance chamber by suitable means, such as a bayonet form ofconnection later described with particular reference to Figure 9. Theresonance chamber itself is divided along its length into three parts I,8 and 9 of which the two end parts 7 and 9 may slide within the centrepart to adjust the length of the chamber, the parts being shown inFigure 1 in the extended position. In this condition parts 1, 8 and 9have an overall length of about 42 inches and the chamber has a diameterof about 11 inches. A second microphone I0 is detachably secured at theclosed end of the part 9 opposite to the loudspeaker and is connectedthrough a suitable amplifier II to photographic recording apparatus l2.

In use the sounds to be transmitted or recorded are first translatedinto electrical impulses by the microphone I which then are amplified bythe amplifier 2 to any desired extent and the amplified sounds arereproduced by the loudspeaker 4 inside the chamber 6. The sounds in thechamher 5 are picked up by the microphone I 0 and after suitableamplification are recorded on the photographic film. Tappings are takenat H to a monitoring device 16 whereby the operator can hear the soundsas they are being recorded and is able to adjust the quality of thesesounds as is required by varying the length of the resonance chamber.

To provide a further means for adjustment of the final sound theloudspeaker 4 is arranged to be readily detachable for interchange witha loudspeaker which may be more particularly suited to an individualartist or sound source.

A further modification of the sound may be effected by placing a screenor screens I4, l5 (for example, of gauze) across the resonance chamber,and screens of different materials may be selected to obtain differentresults. Modifications in the final sound may also be effected byproviding the parts I and 9 of the resonance chamber, with removabletubes, l1 and I8, of materials having any desired sound-absorbingqualities. One such material consists of asbestos fibres held by abituminous binder others are gypsum, marble, cork, treated felt and woodwhich may be perforated or fitted with baffies. The portion 8 is alsopreferably provided with a wrapping of sound-absorbing material as shown.at 18, or by providing a jacket containing a liquid in a manner similarto that later described with reference to Figure 4. This jacket is shownat 30 in Figure 1A.

If desired, two or more resonance chambers and their associatedmicrophones and loudspeakers may be employed for the individualmodification of sounds from different sources which are subsequently tobe combined. In certain cases the adjustment of the resonance chambersmay be inter-connected so that a single control operates the adjustmentof all the chambers.

In the modified form of this arrangement shown in Figure 2 twoloudspeakers 3 and 4 are employed and are detachably secured to the endsof the arms of a tubular Y-shaped member 5 which is secured to the endof the resonance chamber 6 in place of the loudspeaker 4 shown inFigure 1. In this example the loudspeaker 3 (which is also of the typedescribed in my aforesaid United States application Serial No. 748,474)has a driven cone of diameter of about 6% inches and is adapted toreproduce correctly sounds of high frequency while the loudspeaker 4 hasa driven cone of diameter of about 11 inches and is adapted to reproducecorrectly sounds of low frequency. f

The two arms of the Y are arranged to be of equal length. Theloudspeakers are arranged to be readily detachable (for example, bymeans of a bayonet connection) from the Y-shaped member for interchangewith loudspeakers which may be more particularly suited to an individualartist or sound source. Further, the Y-shaped member is arranged forready detachment from the resonance chamber in order that it may bereplaced either by a member of different form (for example, one havingthree arms and three loudspeakers) or by a single loudspeaker.

In the example illustrated in Figures 3 to 9 an arrangement is shownwhich is adapted for use in the photographic recording of sound. Inorder to record simultaneously and in satisfactory balance the soundsfrom a number of different spaced sources on the same set or even fromdifferent sets, or partly from the set and partly from a sound effectsdepartment, a plurality of microphones I are employed, each being placedadjacent to a source of sound (in this case five which may be forexample a chorus, the effects department, a tap dancer, a vocalist andan orchestra). The electrical impulses from each microphone areseparately amplified by means of individual amplifiers 2 and theamplified impulses are arranged to operate a set of loudspeakers 4 eachcorresponding to one of the microphones. These loudspeakers are allarranged to produce sound waves within a single closed chamber 20 at oneend of which is a microphone ll] connected through suitable amplifiersto the photographic recording apparatus. The degree of amplification ofeach of the several amplifiers 2 is separately controllable so that anydesired balance of sound from the various loudspeakers may be obtainedwithin the chamber 20. By this arrangement it is found that the severalsounds can be satisfactorily combined and at the same time proper andfully graduated control of the balance can be obtained.

In'this example the resonance chamber 20 has the shape shown in Figure 4in section the chamber being of bulbous shape with an extending tubularneck and being a solid of revolution about the axis AA with fiveextensions 2| for the loudspeakers 4. These exten sions each have theinternal shape shown in detail in Figure 6 in order to reducereverberation at the entrance to the resonance chamber. The shape of thechamber and the character of the interior walls of the extensions arecalculated and arranged so as to produce desired reflections,absorptions and resonance efiects, whereby predetermined modificationsof the sound in the resonance chamber are acoustically obtained.

The microphone l may be axially adjustable along the mouth of thechamber if desired, and the extensions 2| (which are all identical) withtheir associated loudspeakers are each readily detachable from theresonance chamber in order that a loudspeaker especially suited to anyparticular sound source may be quickly inserted where desired.

The form of connection employed in this example is of the bayonet typeand consists of three tongues 22 formed on the body of the extension andarranged to pass through openings 23 cut in a screwed ring 24 inengagement with a boss 25 on the resonance chamber, and, on rotation ofthe extension, to move under springs 26 (Figure 9) secured to the ring24 up to an abutment 21.

As a further means of controlling, or modifying, the sound from one ormore of the loudspeakers screens (e. g. of perforated metal, velvet orthe like) may be inserted at 28 across the mouth of one or more of theextensionsthe extensions having a diametral slot cut, as indicated, forthe reception of the screens. The

' slots are so arranged that the screens are infilling and emptyingplugs 3| and 32. In use the jacket is filled with different liquids inorder to obtain different results. Alternatively the chamber may be leftunjacketcd and may be coated as required with suitable materials such asa mixture of asbestos fibres with bitumen.

If desired a tapping may be taken oil the leads from the microphone IDin order to provide means whereby the operator may hear the combinedsound and when necessary effect adjustment to the controls.

When it is desired to modify the sounds from each source individuallybefore they are combined the extension 2| may be replaced by tubularmembers which are variable in length. Ihis arrangement is shown inFigure 10 which illustrates a portion of the chamber 20 shown in Figure4 with two of the extensions 28 replaced by extendible members 35. Thesemembers each consist of three portions of which the two end parts mayslide within the centre part in a similar manner to the arrangementshown in Figures 1 and 2. In one case the member is provided with asingle loudspeaker 4 and in the other case with a Y-shaped extensioncarrying at its end two loudspeakers 3 and 4 in a similar manner to thearrangement shown in Figure 2. The members 35 are attached to theresonance chamber by means of bayonet connections of the kind alreadydescribed with particular reference to Figure 9. Screens l4 and I may beinserted across the members 35 in order to provide a further control ofthe quality of the, sound. It is to be understood that any number of theextensions 2| may be replaced by extendible members 35 in this mannerand some of these members may have a single loudspeaker while others maybe arranged to carry two or more loudspeakers as may be desired.

I claim:

1. The method of modifying the tone quality of sounds being transmittedfor recording or reproduction which comprises the steps of initiallyconverting the sound to be recorded into electrical impulses, convertingthe electrical impulses into sound waves in a resonance chamber,selectively modifying the acoustic characteristics of the sound waveswithin said chamber, and re-converting the modified sounds intoelectrical impulses 2. The method of modifying the tone quality ofsounds being transmitted for recording or reproduction which comprisesthe steps of initially converting the sound to be recorded intoelectrical impulses, selectively amplifying said electrical impulses,converting the amplified electrical impulses into sound waves in aresonance chamber, selectively modifying the acoustic characteristics ofthe sound waves within said chamber, and re-converting the modifiedsound waves into electrical impulses.

3. The method of modifying the tone quality of sounds being transmittedfor recording or reproduction which comprises the steps of initiallyconverting the sound to be recorded into electrical impulses, convertingthe electrical impulses into sound waves in a resonance chamber oftubular form, acoustically modifying said sound waves in said chamber byvarying the length thereof, and re-converting the sound waves intoelectrical impulses by means of a microphone located at the other end ofthe resonance chamber.

4. The method of modifying the tone quality of sounds being transmittedfor recording o reproduction which comprises the steps of ini tiallyconverting the sound to be recorded into electrical impulses,selectively amplifying said electrical impulses, converting theamplified electrical impulses into sound waves in a resonance chamber,modifying said sound waves in said chamber by adjusting the reflecting,absorbing and resonant characteristics of the interior walls of saidchamber, and re-converting the sound waves into electrical impulses.

5. The 'method of combining for purposes of simultaneous recording ortransmission by elec trical means sound from a plurality of sourceswhich comprises the steps of converting the sounds from the said sourcesseparably into electrical impulses, separably converting the impulsesfrom each source into sound waves within a single chamber, andre-converting the combined sound waves within the chamber intoelectrical impulses.

6. The method of combining for purposes of simultaneous recording ortransmission by electrical means sounds from a plurality of spacedsources which comprises the steps of converting the sounds from the saidsources separably into electrical impulses, separately amplifying theelectrical impulses corresponding to each source, separately convertingthe amplified impulses from each source into sound waves within a singlechamber, and re-converting the combined sound waves within the chamberinto electrical impulses.

'7. The method of combining for purposes of simultaneous recording ortransmission by electrical means sounds from a plurality of spacedsources which comprises the steps of converting the sounds from the saidsources separately into electrical impulses, separately amplifying theelectrical impulses corresponding to each source to an extent sufficientto produce the desired balance in the final combined sound, separatelyconverting the amplified impulses from each source into sound waveswithin asingle chamber, and re-converting the combined sound waveswithin the chamber into electrical impulses.

8. The method of combining for the purposes of simultaneous recording ortransmission by electrical means sounds from a plurality of spacedsources and of modifying the quality of the sounds which comprises thesteps of converting sounds from said sources separately into electricalimpulses, separately amplifying the electrical impulses corresponding toeach source, separately converting the amplified impulses from eachsource into soundwaves within a single chamber, adjusting the acousticcharacteristics of the chamber, and re-converting the combined soundwaves within the chamber into electrical impulses.

9. The method of combining for the purposes of simultaneous recording ortransmission by electrical means sounds from a plurality of spacedsources which comprises placing a microphone adjacent to each of thesources, amplifying the electrical impulses of each microphoneindividually, converting the amplified impulses int-o sound waves withina single chamber by means of a plurality of loudspeakers eachcorresponding to a different microphone, and reconverting the soundwaves within that chamber into electrical impulses by means of amicrophone.

10. Apparatus for modifying the tone quality of sounds being transmittedas electrical impulses for recording or reproduction, comprising thecombination with microphonic means for receiving and translating soundinto electrical impulses, of a chamber adjustable as to its acousticcharacteristics, a sound-reproducing device associated with said chamberarranged to convert said electrical impulses into sound waves within thechamber, and a microphone arranged to pick up the sound waves within thechamber and to convert them into electrical impulses.

11. Apparatus for modifying the tone quality of sounds being transmittedas electrical impulses for recording or reproduction, comprising thecombination with microphonic means for receiving and translating soundinto electrical impulses, of a chamber adjustable in size, asound-reproducing device associated with said chamber arranged toconvert said electrical impulses into sound waves within the chamber,and a microphone arranged to pick up the sound waves within the chamberand to convert them into electrical impulses.

12. Apparatus for modifying the tone quality of sounds being transmittedas electrical impulses for recording or reproduction, comprising thecombination with microphom'c means for receiving and translating soundinto electrical impulses, of a chamber adjustable in size to vary itsacoustic characteristics and provided with a removable sound absorbinglining, a loudspeaker within the chamber, and a microphone also withinthe chamber.

13. Apparatus for modifying the tone quality of sounds being transmittedas electrical impulses for recording or reproduction, comprising thecombination with microphonic means for receiving and translating soundinto electrical impulses, of a chamber of tubular form and adjustable inlength to vary its acoustic characteristics and provided with aremovable screen and lining, a loudspeaker located at one end of thechamber, and a microphone located at the other end of the chamber.

14. Apparatus for modifying the tone quality of sounds being transmittedas electrical impulses for recording or reproduction, comprising thecombination with microphonic means for receiving and translating soundinto electrical impulses, of a resonance chamber adjustable as to itsacoustic characteristics, a removable loudspeaker within the chamber,and a removable microphone also within the chamber.

15. Apparatus for modifying the tone quality of sounds being transmittedas electrical impulses for recording or reproduction, comprising thecombination with microphonic means for receiving and translating soundinto electrical impulses, of a tubular resonance chamber, a movablescreen within the chamber and arranged to modify the acousticcharacteristics thereof, a removable sound-reproducing device arrangedto convert the electrical impulses into sound waves associated with oneend of said chamber, and a removable microphone arranged to pick up thesound waves associated with the other end of said chamber and tore-convert said sound waves into electrical impulses.

16. Apparatus for use in combining for purposes of simultaneousrecording or transmission by electrical means sounds from a plurality ofspaced sources comprising a plurality of microphones placed adjacent tothe several sourcesrespectively, amplifiers arranged to amplify theelectrical impulses from each microphone individually, a chamber, aplurality of loudspeakers each arranged to convert the amplifiedimpulses from a different microphone into sound waves within thechamber, electrical connections between the microphones, amplifiers andloudspeakers and a microphone arranged to pick up the sound waves withinthe chamber.

17. Apparatus for use in combining for purposes of simultaneousrecording or transmission by electrical means sounds from a plurality ofspaced sources comprising aplurality of microphones placed adjacent tothe several sources respectively, amplifiers arranged to amplify theelectrical impulses from each microphone individually and separatelyadjustable as to their degree of amplification, a chamber, a pluralityof loudspeakers each arranged to convert the amplified impulses from adifierent microphone into sound waves within the chamber, electricalconnections between the microphones, amplifiers and loudspeakers and amicrophone arranged to pick up the sound waves within the chamber.

18. Apparatus for modifying the tone quality of sounds being transmittedas electrical impulses for recording or reproduction and comprising incombination a microphone located adjacent to a sound source, anamplifier, a telescoping resonance chamber adjustable so as to vary itsacoustic characteristics, a plurality of loudspeakers within the chamberand having different sound-reproducing characteristics, electricalconnections from the microphone and amplifier to the loudspeakers, and amicrophone arranged to pick up sound waves within the chamber.

' 19. Apparatus for use in combining for purposes of simultaneousrecording or transmission by electricalmeans sounds from a plurality ofspaced sources comprising a plurality of microphones placed adjacent tothe several sources respectively, amplifiers arranged to amplify theelectrical impulses from each microphone individually, a chamber, aplurality of loudspeakers each arranged to convert the amplifiedimpulses from one of the microphones into sound waves within thechamber, electrical connections between the microphones, amplifiers,loudspeakers, a microphone arranged to pick up sound waves within thechamber, reproducing apparatus, and electrical connection from themicrophone to the reproducing apparatus.

20. Apparatus for use in combining for purposes of simultaneousrecording or transmission by electrical means sounds from a plurality ofspaced sources comprising a plurality of microphones placed adjacent tothe several sources respectively, amplifiers arranged to amplify theelectrical impulses from each microphone individually, a chamber, aplurality of loudspeakers each arranged to convert the amplifiedimpulses from one of the microphones into sound waves within thechamber, electrical connections between the microphones, amplifiers,loudspeakers, a microphone arranged to pick up sound waves within thechamber, reproducing apparatus, electrical connections from themicrophone to the reproducing apparatus, and a tapping from theseconnections to a monitoring device.

21. Apparatus for modifying the tone quality of sounds being transmittedas electrical impulses for recording or reproduction and comprising aresonance chamber of tubular form and adjustable in length to vary itsacoustic characteristics, a Y-shaped extension on one end of the tubularchamber, two loudspeakers having different sound-reproducingcharacteristics and located respectively at the ends of the arms of theY-shaped extension, and a microphone located at the opposite. end of thechamber from the Y-shaped extension.

22. Apparatus for use in combining for purposes of simultaneousrecording or transmission by electrical means sounds from a plurality ofspaced sources comprising a bulbous chamber having a tubular neck, and aplurality of tubular extensions from the bulbous portion, a loudspeakerat the outer end of each extension, and a microphone within the tubularneck.

23. Apparatus according to claim 22, in which the tubular extensions areprovided with means whereby they are individually adjustable as to theiracoustic characteristics.

24. Apparatus for modifying the tone quality of sounds being transmittedas electrical impulses for recording or reproduction and comprising incombination a chamber of adjustable length, a removable lining for saidchamber arranged to vary the acoustic characteristics of the chamber, asound reproducing device arranged to convert electrical impulses intosound waves within the chamber, and a microphone arranged to pick up thesound waves within the chamber and to convert them into electricalimpulses.

25. Apparatus for modifying the tone quality of sounds being transmittedas electrical impulses for recording or reproduction and com prising atubular chamber, a detachable and interchangeable tubular lining for apart of the chamber, a loudspeaker located at one end of the chamber,and a microphone located at the other end of the chamber.

ROBERT RODGER GLEN.

